The present invention relates to an improved laundry washing machine.
It is underlined that in the present application the expression “washing machine” may as well indicate a “simple” washing machine (i.e. a washing machine which can only wash and rinse the laundry) and a washing-drying machine (i.e. a washing machine which can also dry the laundry), both of the front-loading type and of the top-loading type.
Nowadays washing machines generally comprise an external casing provided with a loading/unloading door which allows the access to a washing tub containing a rotatable washing drum in which the laundry to be washed can be loaded.
These known washing machines are adapted to perform washing cycles comprising one or more phases, for example a soaking phase, a main wash phase (comprising, for example, the adduction into the washing tub of water mixed with detergent and the rotation of the drum, so as to apply a mechanical action on the laundry), a steam supplying phase, a rinsing phase, a spinning phase, etc.
These known washing machines comprise also a user interface adapted for allowing a user to set a washing programme to which corresponds a washing cycle to be performed; depending on the specific washing programme set by the user, during a same washing cycle the above mentioned phases of the washing cycle (and/or other phases which have not been mentioned) may be not performed, or performed only once, or also performed two or more times (for example the rinsing phase is typically performed two or more times during a same washing cycle).
Some known washing machines are also provided with a weight sensing device adapted to sense the weight of the laundry which is loaded in the washing drum.
For example GB 2225030 discloses a domestic washing machine comprising a tub suspended resiliently relatively to a mounting frame by a suspension spring. A toroidal coil is connected, via a suspension, to the frame of the washing machine; this coil surrounds concentrically the suspension spring. A coil core is rigidly secured to the tub, inside the suspension spring or surrounding it concentrically; therefore, as the loading of the washing (i.e. the laundry to be washed) increases, the coil core can move downwards with the tub, vertically in the magnetic field of the energized coil, in accordance with the characteristic of the suspension spring. As a result of the change in the position of the magnetizable coil core inside the energized toroidal coil, the magnetic flux is altered considerably. This change in the magnetic flux is converted into signals through electronics, and indicates the weight of the washing introduced into the drum at an indicator window via a plurality of light-emitting diodes or directly via a digital display.
After knowing the weight of the laundry loaded into the washing machine, the user may select the washing program and the quantity of detergent which best fits this quantity of laundry.
This known washing machine, however, isn't adapted to automatically modify the duration of the washing cycle according to the weight of the loaded laundry; for example this known washing machine isn't adapted to automatically reduce the number of rinses in a washing cycle if it detects that the quantity of loaded laundry is small (in which case it would be sufficient a reduced washing/rinsing duration). This fact leads to wastage of energy and time if the quantity of laundry to be washed is small.
Another example of known washing machine provided with a device for detecting the weight of the laundry loaded into the washing drum is shown in EP 0051491 which discloses a washing machine having its drum/drive mechanism and the tub assembly mounted upon transducers which provide an indication of the weight of the mechanism and assembly, and of the weight of articles loaded into the drum for washing. The transducers input to a microprocessor which determines the weight of the clothes and also the weight of water required to wash that weight of clothes under program conditions, some at least of which are selected by the user. The microprocessor may also control a display which indicates the amount of detergent required. In one embodiment of the invention, the control system of the washing machine is adapted to indicate to the user when the weight of articles loaded into the machine exceeds the maximum weight appropriate to a selected program. It is also disclosed that where a small load of articles is to be dealt with, the control system may be adapted to reduce the number of rinse stages.
However this known washing machine modifies at most the number of rinses if the quantity of laundry is small, but it doesn't modify the number of repetition nor the duration of the other phases of the washing cycle (for example the warming of washing water, the soaking phase, the stirring phase, etc.), and therefore there is the risk, for example, that the duration of one or more of such other phases would be too long for the loaded quantity of laundry, and/or that one or more phases would be repeated too many times, which would lead to wastage of energy and of time.
Moreover this known washing machine may modify the number of rinses, and therefore the duration of the overall washing cycle, but it isn't adapted to inform the user of this modified duration.
A known washing machine comprising the feature of calculating the duration of the washing cycle as a function of the sensed weight of the loaded laundry, and of informing a user about this duration is illustrated for example in EP 1029964; this document discloses a washing machine, in particular a domestic washing machine, having a control panel in which are disposed a programme selection device for setting a wash programme which is dependent upon the washing type. The washing machine is provided with a display device for presenting user information. The washing machine comprises a rotatable drum for receiving washing (i.e. the laundry to be washed), and a sensor for detecting the weight of the washing situated in the drum. The washing machine comprises also a microprocessor control which calculates state variables and user information dependent upon the weight detected by the sensor, and which actuates the display device with these variables and information. The washing machine comprises a first memory, which is integrated into the microprocessor control, for storing first memory values in the form of permissible maximum weights which are associated with each wash programme or respectively with the washing type associated with the wash program. This washing machine comprises a second memory for storing second memory values in the form of detergent desired quantities, and also a third memory for storing values in the form of programme running times. The second and third memory values are associated respectively with a wash programme or respectively with the washing type associated with the wash programme and with a washing weight. The washing machine comprises an evaluation circuit, which is integrated into the microprocessor control, for retrieving the first, second, and third memory values dependent upon the weight of the washing detected by the sensor and upon the weight of the washing detected by the sensor and upon the set wash programme and for calculating first, second and third display values from the respective memory values. The washing machine comprises a display device having a first display part and a second display part. In the first display part the filing level of the drum as first display value, the detergent desired quantity as second display value, and the programme running time as a third display value, are presented in succession. In the second display part, the type of respective display value of the microprocessor control is presented. In particular this document discloses a loading procedure wherein, during the loading of the laundry into the drum, the weight of the laundry is detected and is shown in the display; when the door is closed, and therefore the loading procedure is terminated, the display ends showing the weight of the laundry, and starts showing the detergent quantity which is needed for a selected kind of laundry and for the sensed weight of the laundry. By operation of a start button the wash program starts, and the display starts showing the remaining time (i.e. the time required until the end of the washing cycle); the indicated remaining time becomes down-counted in the course of the wash program.
Also this known solution has however a drawback; in fact the user may know the time remaining to the end of the washing cycle only after finishing loading the laundry and closing the door; if the duration of the washing cycle indicated in the display after the closure of the door is different (for example higher) from the duration desired by the user (for example because the user needs removing the laundry from the washing machine by a certain time), in order to modify this duration the user has firstly to open the door, then to modify the amount of laundry loaded into the drum, successively to close again the door, and finally to verify once more the remaining time indicated in the display. The user has to repeat this procedure until reaching the desired value of the remaining time. It is clear that this procedure may be unpleasant, and it also increases the time required to load the washing machine before starting the washing cycle.
DE 199 46 245 C2 discloses a method for controlling a washing program of a washing machine with an outer tub pivotally suspended or supported on springs, in which an inner drum for accommodating laundry is rotatably mounted and can be actuated by a motor; the washing program is controlled with respect to washing parameters such as water consumption, wash duration, number of rinsing cycles and/or the spinning speed profile and/or with respect to user information which can be displayed by display elements of the washing machine. The control is executed subject to a measured laundry weight value determined by a weight sensor on the basis of the weight-related lowering of the outer tub before water is added to the outer tub. The method described in this document comprises the following methodological steps: —the program control system determines a subsequent measured value that depends on the type and the weight of the laundry located in the drum; —computation of the actual weight of the laundry on the basis of the measured laundry weight value and the subsequent measured value by a correction circuit integrated in the program control system; —the program control system proceeds with the wash program using washing parameters dependent upon the actual weight of the laundry. In one embodiment of the method, the subsequent measured value is determined by the program control system on the basis of the suction response after the water has flowed into the outer tub.
U.S. Pat. No. 4,235,085 discloses an automatic vertical axis washer designed to detect a charged quantity of material of washing, and to carry out the respective steps of washing (including rinsing and dehydration) only for a length of time corresponding to the detected quantity. The automatic washer comprises drive means for rotating a stirring blade member or a dehydration tub, and control means connected to the drive means to carry out the respective operation steps of the washer for lengths of time determined by a signal denoting a charged quantity of material which is issued during a washing cycle in accordance with the rotation characteristic of the drive means.
U.S. Pat. No. 4,553,413 discloses a vertical axis washing machine adapted to detect the washing load size in terms of instantaneous variations in such values as the rpm of the agitator and motor current by making use of the fact that the motor load acts discontinuously and instantaneously owing to the movement of the washing load in the washing machine toward and away from the agitator, the size of the resulting detection signal being utilized to control the washing process, making it possible to properly set the washing bath ratio, detergent concentration, washing time, and agitator drive period.
FR 2 577 949 A1 discloses a machine for washing and for spin-drying laundry comprising a means for automatically making the spin-drying duration, in the course of the rinsing phase and/or in the course of the final spin-drying, dependent on at least one of the following parameters: the amount of laundry introduced into the drum, the type of this laundry, and the rotational speed of the drum. In order to determine the load of laundry, i.e. the percentage of the volume of the drum that is occupied by the laundry, a means is provided for measuring the moment of inertia of the laundry relative to the axis of rotation of the drum; for this measurement, the drive torque of the drum at constant acceleration of the drum is determined. Thus, before being filled with water, the drum, filled with dry laundry, is made to rotate at constant known acceleration and the (drum drive) motor torque, which is proportional, to within one constant, to the moment of inertia, is measured. It is disclosed that if a universal motor is used to make the drum rotate and if this motor is powered at constant voltage, it is sufficient to measure the intensity of the current passing through the motor—which is a linear function of the motor torque—in order to obtain a linear representation of the moment of inertia.